The present invention relates to magnetic tape cassettes, and more particularly to an audio compact cassette which is the same in size or smaller than a standard "Phillips"-type compact cassette.
Recently, cassette tape recorders have been reduced both in size and in weight, and accordingly it is desirable that magnetic tape cassettes used for such recorders also be miniaturized. Therefore, there has been a strong demand for the provision of small magnetic tape cassettes which are suitable for high-quality and high-density recording and reproducing operations.
Magnetic tape cassettes meeting this requirement are often recorded on using a digital recording system such as the PCM (pulse code modulation) system whereby recording and reproducing operations are carried out with input signals converted into pulse signals. In such a system, the recording frequency bandwidth must be about five times that which a conventional audio tape is capable of. Therefore, video tape cassettes have been extensively employed for digital recording.
Video tape cassettes (except for special cases) are employed with a recording/reproducing apparatus using a rotary head system. These video tape cassettes have guard panels which close openings in the front parts of the cassettes when the cassettes are not in use, and which are swingable upwardly to gain access to the tape for recording/reproducing. That is, because in a digital recording/reproducing system, recording is carried out at a high density and using a wide bandwidth, to maintain its suitability for such use, the magnetic tape cassette must have provisions for preventing the entrance of dust and for protecting the magnetic tape from damage.
The technical concept of the invention is particularly applied to a very small magnetic tape cassette which, as in the case of a video tape cassette, employs a relatively wide bandwidth recording and reproducing system, and which is applicable to audio devices, and which is the same in size or smaller than the conventional audio compact cassette.
As in the conventional audio magnetic tape cassette, the digital audio magnetic tape cassette should be suitable for use outdoors and it should be possible to transport the cassette without its storage casing.
A variety of digital audio type magnetic tape cassettes have been proposed in the art. Such a magnetic tape cassette generally includes a guard panel which can be swung upwardly, similar to the above-described video tape cassette, and a slide guard which can be slid back and forth on the bottom of the cassette thereby to close the lower part of the opening formed in the front part of the cassette.
However, conventional digital audio magnetic tape cassettes of this type are relatively intricate in construction and more difficult to assemble than video cassettes due to their smaller size and weight. These problems are exacerbated due to the presence of components such as the slide guard, a hub locking member, and an urging member for operating these components.
Furthermore, in view of the foregoing, it is essential that the digital audio magnetic tape cassette provide more positive protection and dustproofing of the magnetic tape than the conventional video tape cassette. Also there has been a strong demand for the provision of a slide guard for the cassette which can more smoothly slide.